Adeno-associated virus (AAV) is a 5 kb nonpathogenic, helper dependent member of the Parvovirus Family. The adeno-associated virus (AAV) genome is built of single-stranded deoxyribonucleic acid (ssDNA), either positive- or negative-sensed, and comprises inverted terminal repeats (ITRs) at both ends of the DNA strand, and two open reading frames (ORFs): rep and cap. Rep is composed of four overlapping genes encoding rep proteins required for the AAV life cycle, and cap contains overlapping nucleotide sequences of capsid proteins: VP1, VP2 and VP3, which interact together to form a capsid of an icosahedral symmetry.
Typically, AAV has been utilized as a viral vector by removing endogenous AAV genes, substituting a gene of interest, encapsidating with Ad or herpes simplex (HSV), and purifying the vector away from the helper virus. However, without its endogenous genes, there is limited potential for producing a sufficient amount of the AAV vectors for therapeutic uses. For this and other reasons, it would be beneficial to design an AAV vector that includes endogenous AAV genes.